Compositions for sealing pavement

ABSTRACT

Compositions comprising cut-back, air-blown asphalt, asbestos fibers and fluidized coke derived from the refining of heavy crude oils when used to seal pavement surfaces display improved anti-skid properties and resistance to wear.

United States Patent [1 1 Draper et al.

11 3,801,341 [451 Ap r.2, 1974 COMPOSITIONS FOR SEALING PAVEMENT [75] Inventors: Homer L. Draper; Duane W. Gagle,

- both of Bartlesville, Okla.

[73] Assignee: Phillips Petroleum Company, Bartlesville, Okla.

[22] Filed: Sept. 17, 1971 [21] Appl. No.: 181,596

[52] U5. Cl 106/282, 106/280, 106/281, 106/284 [51] Int. Cl.. C08h 13/00, C08h 17/08, C08h 17/22 [58] Field of Search 106/280-284, 106/38.8; 94/9, 20, 22, 23

[56] References Cited UNITED STATES PATENTS 2,157,696 5/1939 Greider et al 106/282 X 2,546,659 3/1951 Sussenbach 106/282 X 3,239,361 3/1966 Speer 106/275 3,615,803 10/1971 Draper et a1 106/282 X 3,567,660 3/1971 Winkler 106/282 X Primary Examiner-James A. Seidleck Assistant Examiner-John Kight, III

[5 7] ABSTRACT 6 Claims, No Drawings COMPOSITIONS FOR SEALING PAVEMENT BACKGROUND OF THE INVENTION This invention relates to asphalt containing compositions suitable for use as pavement sealers. In still another aspect, this invention relates to pavement sealing compositions containing air-blown asphalt, asbestos fibers and fluidized coke.

The use of asphalt containing compositions as pavement sealers for highways and airport runways is well known in the art. These pavement sealers are generally used to recondition the wear surface of the highway or runway when exposure to weather and traffic has led to deterioration. In the case of asphalt surfaces, the loss of volatile components and oxidative processes result in the asphalt becoming hard and brittle. Cracks develop which allow the introduction of water. During cold weather, alternate freezing and thawing of this water will enlarge the cracks. If steps are not taken to alleviate this condition, the damage will become so severe as to lead to complete failure of the surface which results in the formation of pot holes. To avoid this problem the pavement sealer is applied before deterioration is severe and prevents further damage by filling the cracks in the old surface.

Since the sealing compositions are applied in relatively thin layers and withoutaggregate, the resulting surface is quite smooth. Thus, during rainstorms and for a time thereafter until the pavement dries, the surface is quite slippery. The likelihood that vehicles using the surface will become involved in skids, of course, in-

creases.

In the past it has been proposed to alleviate this problem by incorporating in the pavement itself ground glass and other abrasives. However, this has not proved to be satisfactory for a number of reasons including the general incompatibility of these abrasives with the asphalt compositions into which they are incorporated and the high cost involved in using large amounts of glass and abrasives. Also, these materials adversely affect tires by increasing the amount of wear because of their exterior hardness.

In order to exhibit the required resilience that makes possible its use as a pavement material, the pavement sealers are necessarily soft. This softness increases the propensity of the asphalt to wear under conditions of heavy traffic, thus shortening the effective lifetime of the pavement sealer and necessitating reapplication.

These and related problems are ameliorated through use of the compositions of this invention.

SUMMARY OF THE INVENTION It is an object of this invention to provide novel asphalt compositions useful as pavement sealers.

It is another object of this invention to provide pavement sealers having improved anti-skid properties and resistance to wear.

In accordance with this invention we have found that a composition comprising a cut-back, air-blown asphalt, asbestos fibers and fluidized coke derived as the residual coke from petroleum refinery operations when applied as a pavement sealer has, after curing, improved anti-skid properties and resistance to wear.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The compositions of this invention generally comprise a mixture of cut-back, air-blown asphalt, asbestos fibers and a hard fluidized coke.

The air-blown asphalts useful in these compositions are those derived from the asphaltic residua of refinery processes. The manner of producing these is well known to those skilled in the art. Generally, they are prepared by contacting the particular asphaltic residuum with air at temperatures ranging from 400550F. A variation of air-blowing process involves employing a catalyst to reduce the time required to achieve the desired degree of modification of the properties of the base asphalt. Typical catalysts include ferric chloride, phosphorus pentoxide, and zinc chloride although others are known.

The asphalts useful in the compositions of this invention may be characterized by a number of standard tests. Among these are ring and ball softening point as determined by ASTM D36 and penetration value as determined by ASTM D5. Those air-blown asphalts which can be used in this invention can have a ring and ball softening point from about 1 l0220F, with a penetration value at 77F ranging from about 15 to about 150. Since the compositions are to be employed as pavement sealers, the preferred asphalts have a ring and ball softening point from about -l85F and have a penetration value at 77F ranging from about 25-45.

The air-blown asphalt is dissolved in a suitable cutback solvent to facilitate mixing with other ingredients and application to the desired surface. Since it is eventually allowed to evaporate, the selection of a particular cutback solvent is within the skill of one knowledgeable in the art. Suitable solvents are generally selected from hydrocarbons and halohydrocarbons.

The solvent actually employed is generally selected on the basis of its boiling point (or boiling point range if a mixture of compounds). When it is desired that the treated surface be available for use quickly, a solvent of relatively high volatility (low boiling point) is selected. This allows for rapid evaporation or curing as it is referred to by those skilled in the art. When, for one reason or another, a slower cure is desired solvents of low volatility are employed.

Typical solvents used for rapid curing include, but are not limited to, benzene, toluene, the xylenes, naphtha (boiling point range 275-425F), carbon tetrachloride and methylene dichloride. Solvents for slow cure include kerosene and crude oil residua of suitable viscosity. The actual cut-back solvent for the test samples of this invention is a naphtha having a boiling point range from 275425F.

The asbestos component of these novel compositions should be in the form of asbestos fibers. Although the length of suitable fibers can vary over a wide range, it is preferred to use relatively fine fibers in order to facilitate formation of a homogeneous mixture and to ease spreading since normally application on a large scale will be done by spraying. Commercially available asphalt fibers do not come in uniform lengths. However, the fibers for use in this invention can be characterized according to the ROTAP screen analysis test of the Quebec Asbestos Mining Association. Of those fibers preferred for use in compositions of this invention, essentially I00 weight percent will pass through a 6-mesh screen, but nor more than about 30 weight percent pass through a 65-mesh screen determined by ROTAP screen analysis. A source of asbestos fibers having ROTAP Screen Analysis (100 gms 30 mins.)

Plus 6 mesh Plus l4 0 Plus 20 4 Plus 23 43 Plus 35 25 Plus 65 9 Minus 65 19 The residual coke suitable for use in this invention is that termed fluidized coke and is derived from petroleum refinery operations that are well known.

Residual cokes are of two types. Some well-known petroleum refinery operations result in the formation of a residual material termed delayed coke. Delayed coke differs from fluidized coke in a number of physical properties and is not suitable for use in the compositions of this invention.

Delayed coke, in general, is a lumpy, black, porous substance resembling coal coke. In size, delayed coke may range from chunks measuring a foot or more in width to particles small enough to pass through a 200- mesh screen. However, delayed cokes are usually broken into irregular pieces ranging from that of a walnut to that of a baseball.

On the other hand, fluidized coke is strikingly different in appearance. It is a small-particled, easily flowing mass somewhat like black sand. The particle sizes, though characteristically small, are assorted, ranging from that of a pinhead to a pea in size. The shape of the particles is usually spherical to subspherical often with berry-like nodules on the surface.

Fluidized coke pours and flows easily and is cleaner than most carbonaceous materials. It is harder and more resistant to attrition than delayed coke.

Representative analyses of a typical example of de layed coke and of fluidized coke, taken from the Bureau of Mines Information Circular IC 8259 entitled Petroleum Coke on the West Coast of the United States by W. J. Kemnitzer, et al, are given below:

Delayed Coke Fluidized Coke Volatile Matter Wt. 12.0 4.0

(including moisture) Fixed Carbon Wt. 86.4 89.8 Sulfur Wt. L! 5.8 Other Wt. 0.6 0.7

The residual coke used in the compositions of this inveution is the fluidized coke derived from the refining of heavy crude oils having an API gravity varying over the range from about 8-l2. A typical crude oil having an API gravity in this range is the well-known California heavy crude. Compared to other delayed cokes, which are relatively soft, the coke derived from these heavy crudes is quite hard.

A typical coke derived from such a heavy crude oil and used in the sample compositions forming a part of this application has the following elemental analysis:

Wt. Percent Atomic Ratio Carbon 88.8 10 Hydrogen 2.5 3.1 Sulfur 2.5 0.1 Ash 6.2

The residues appeared to be ash, but may, in part, be combined oxygen and/or nitrogen.

Examination of the granules of this coke using a scanning electron microscope showed it to have a smooth surface. At high magnification, observation indicated few, if any, internal voids of greater than one micron.

The coke is entirely non-crystalline as evidenced by X-ray diffraction. The only peak of significance corresponds to a spacing of 3.55 Angstroms. This is approximately the sheet to sheet distance usually found in carbon black, but the diffraction pattern lacked the intense low angle scattering typical of a carbon black-like sheet structure. Thus, the coke appears to be more disorganized than carbon black and appears to be an amorphous carbon glass.

Before use in the compositions of this application, the coke should be screened to remove excessively large particles. Preferably, percent of the coke employed will pass a No. 10 mesh screen. A sample of coke actually used in the samples forming a part of this application had the following sieve analysis:

The air-blown asphalt, in a suitable cut-back solvent, asbestos fibers and fluidized coke can be blended using any of a number of techniques well known to those skilled in the art of compounding asphalt with other materials. One suitable apparatus for this purpose is a pug mill.

For use as a pavement sealer, the ingredients should naturally be combined in such proportions that, after evaporation of the cut-back solvent, the resulting pavement surface meets applicable state or local standards for softening point and penetration value and the abrasiveness as imparted by the fluidized coke is at the desired level.

The compositions of this invention ordinarily will comprise a major portion of cutback air-blown asphalt and minor portions of the asbestos fibers and fluidized coke. For the usual application to which these compositions will be put, 100 parts by weight of the cutback air-blown asphalt can be combined with up to 8 parts by weight of the asbestos fibers and up to 5 parts by weight of the fluidized coke.

We have found that a combination of 100 parts by weight of a cut-back air-blown asphalt comprising 55-75 parts air-blown asphalt and 25-45 parts of a cutback solvent in combination with 3-8 parts by weight of the asbestos fiber and 2-5 parts by weight of the fluidized coke can be readily applied to a pavement surface by spraying or other suitable means. After curing, i.e., evaporation of the cut-back solvent, the resulting pavement sealing material possesses a higher ring and ball softening point and a lower penetration value as well as improved anti-skid properties and wear resistance as compared to the base asphalt itself and insofar as these properties are concerned meets generally applicable standards.

EXAMPLE A cut-back, air-blown asphalt was blended with one or both of the ingredients asbestos fibers and fluidized coke. The resulting mixtures were cured in an oven at 140F for 24 hours and comparison tests made with the cured base asphalt without other ingredients. The result of these comparisons is set out in Table 1 below.

TABLE 1 Parts by Weight Penetration Softening Asphalt Solvent Asbestos Coke Value Point From these data it can be seen that the incorporation of asbestos and the fluidized coke raises the softening point and lowers the penetration value of the base asphalt. This has the advantage of improving the wear resistance of these compositions when employed as a pavement sealer. The fluidized coke, which provides the anti-skid properties and also aids in improving resistance to wear, when compared to glass or other abrasives has the advantage of being more compatible with asphalt.

In actual practice, the pavement sealing composition will be applied to a surface and allowed to cure at ambient temperature. The length of time required will depend'upon the cut-back solvent employed. Using naphtha having a boiling point range from 275-425F, 12 hours is generally sufficient when daytime temperatures reach XF.

For test purposes, a mixture comprising 65 parts by weight of an air-blown asphalt having a softening point of l50-185F and penetration value at 77F of 25-40 in 35 parts by weight naphtha (boiling point range 270-425F), 5 parts by weight of asbestos fibers and 3 parts by weight of fluidized coke was diluted with 5 parts by weight Stoddard solvent (boiling point 300-400F) to reduce the viscosity and make spreading easier. This mixture was applied by squeegee to a clean and dry airport runway surface at a rate of 0.22 gallons per square yard. The sealed surface was allowed to cure for 12 hours before exposure to traffic.

A periodic examination of the runway surface over the course of a year has indicated that it remained in excellent condition with no signs of deterioration.

We claim:

1. A pavement sealing composition that can be readily applied to a pavement surface by spraying or other suitable means comprising:

a. parts by weight of a cutback, air-blown asphalt comprising 55-75 parts by weight air-blown asphalt having a ring and ball softening point varying over the range of -220F and a penetration value at 77F varying over the range 15-150 and 25-45 parts by weight of cutback'solvent,

b. 3-8 parts by weight asbestos fibers of such a size that 100 percent pass through a IO-mesh screen, but no more than 10 percent pass through a 65- mesh screen according to the ROTAP screen analysis test, and

c. 2-5 parts by weight of small particled, easyflowing, fluidized noncrystalline coke.

2. A composition according to claim 1 wherein said fluidized coke is an amorphous carbon glass substantially without internal voids greater than one micron and has at 3.55 Angstroms its only significant X-ray diffraction peak.

3. A composition according to claim 1 comprising 65 parts by weight air-blown asphalt, 35 parts by weight of cutback solvent, 5 parts by weight asbestos fibers, and 3 parts by weight of fluidized coke.

4. The cured composition of claim 1.

5. A composition according to claim 1 wherein said fluidized coke is derived from heavy crude oil having an AP] gravity of 8-12 and said cutback solvent is a naphtha having a boiling point range from 275-425F.

6. A composition according to claim 1 wherein said cutback solvent is selected from hydrocarbons comprising benzene, toluene, xylenes, naphthas, kerosene, and crude oil residua or carbon tetrachloride or methylene dichloride. 

2. A composition according to claim 1 wherein said fluidized coke is an amorphous carbon glass substantially without internal voids greater than one micron and has at 3.55 Angstroms its only significant X-ray diffraction peak.
 3. A composition according to claim 1 comprising 65 parts by weight air-blown asphalt, 35 parts by weight of cutback solvent, 5 parts by weight asbestos fibers, and 3 parts by weight of fluidized coke.
 4. The cured composition of claim
 1. 5. A composition according to claim 1 wherein said fluidized coke is derived from heavy crude oil having an API gravity of 8-12 and said cutback solvent is a naphtha having a boiling point range from 275*-425*F.
 6. A composition according to claim 1 wherein said cutback solvent is selected from hydrocarbons comprising benzene, toluene, xylenes, naphthas, kerosene, and crude oil residua or carbon tetrachloride or methylene dichloride. 